Download Auditory Perception and Cognition—A.J. Oxenham

Chapter 38. Auditory Perception and Cognition
Auditory Perception and Cognition
RLE Groups
Auditory Perception and Cognition Group, Sensory Communication Group
Academic and Research Staff
Dr. Andrew J. Oxenham (PI), Dr. Alexander Gutschalk, Dr. Christophe Micheyl, Dr. Andrea
Simonson, Dr. Xuedong Zhang, Ms. Lorraine Delhorne
Graduate Students
Michael Qin, Joshua Bernstein, Craig Lewiston, Courtenay Wilson, Anna Dreyer
Technical and Support Staff
Joseph Frisbie
1. Peripheral interactions in auditory temporal processing
Sponsors
National Institutes of Health, National Institute on Deafness and other Communication Disorders
(NIDCD) – R01 DC 03909
Project Staff
Andrew Oxenham, Andrea Simonson, Xuedong Zhang, Lorraine Delhorne, Joseph Frisbie
A. Auditory filter shapes at low frequencies
We recently established two important findings on frequency tuning in the human inner ear. First,
tuning was sharper than previously thought, and sharpened considerably with increasing
frequency from 1000 to 8000 Hz; second, human tuning was sharper by a factor of two than that
found in other mammals that are often used as models of human hearing (Shera, Guinan &
Oxenham, 2002; PNAS 99:3318-23). The technique used that in that study was suitable only for
frequencies at and above 1000 Hz. Important speech information is carried at lower frequencies,
particularly when the speech is mixed with interfering sources. We have therefore developed a
behavioral technique that allows us to estimate human filter shapes at lower frequencies. We find
that the divergence between our new measures and the earlier estimates of filter tuning are less
at low than at high frequencies and we are now in the position to provide a complete estimate of
low-level human cochlear filter tuning from 250 Hz to 8000 Hz.
B. Changes in cochlear tuning with level
It has been known since the early days of hearing research that the auditory system has many
nonlinearities. One of the most well-known is the deterioration of cochlear tuning at high levels.
It remains unknown how much of the deterioration in tuning is because of a broadening of the
response area of individual primary auditory neurons (or places along the basilar membrane), and
how much is because of nonlinear suppression effects that can strongly affect behavioral tuning
estimates when the masker and probe are presented at the same time. We have addressed this
issue by using non-simultaneous masking to measure cochlear tuning as a function of the probe
frequency. We find that tuning is strongly level dependent at higher signal frequency of 4000 Hz
and above, but essentially independent of level for low and medium stimulation levels at 1000 Hz.
The results, along with those of Sect. 1A, provide important new data and constraints for
computational models of human cochlear filtering, which will be important in a variety of
applications, including audio compression and automatic speech recognition systems.
C. Refining measures of cochlear compression in normal and impaired hearing: Additivity
and sub-threshold masking effects
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Chapter 38. Auditory Perception and Cognition
Earlier work from our group demonstrated that it is possible to derive a behavioral measure of the
input-output function of the cochlea’s basilar membrane. This has potential as a clinical tool,
because reduced compression in the input-output function is a common feature of hearing loss,
and one which may require different medical intervention than a loss related more to
sensorineural transduction abnormalities. The disadvantage of our current techniques is that they
are too time-consuming to be practical in a clinical setting. We have been working on new
techniques that provide similar outcomes in much short time spans. This work has involved
devising new methods and validating them against more established, but more time-consuming,
methods. We have concentrated on tasks involving the additivity of two independent maskers.
As a by-product of this research, we have discovered that a masker, which itself is inaudible, can
have significant masking effects that are well-predicted by a theory of linear summation of neural
events.
2. Complex pitch perception in complex environments
Sponsors
National Institutes of Health, National Institute on Deafness and other Communication Disorders
(NIDCD) – R01 DC 05216
Project Staff
Andrew Oxenham, Joshua Bernstein, Joseph Frisbie, Christophe Micheyl, Michael Qin, Craig
Lewiston, Courtenay Wilson, Anna Dreyer
A. Exploring the relationship between complex pitch perception and frequency selectivity
in normal and impaired hearing
In pitch perception there is a strong dichotomy between the pitch strength (or salience) produced
by low-order harmonics, which are thought to be peripherally resolved, and high-order harmonics
(with harmonic numbers greater than 10), which are considered to be unresolved. The question
we address here is how tight the relationship is between pitch salience (assessed indirectly using
fundamental frequency difference limens – F0DLs) and the peripheral resolvability of the
harmonics. In normal-hearing listeners, F0DLs were measured as a function of F0 for bandpassfiltered harmonic tone complexes, embedded in a background noise that was designed to
maintain each component at a fixed sensation level, and to rule out the perception of distortion
products. At low and medium sound levels, as found in previous studies, there was a dramatic
deterioration in performance as F0 decreased to a point where only harmonics above the 10th
were present in the passband. However, at high sound levels, the deterioration occurred at a
higher F0 (or lower harmonic number). To see whether this change with level related to changes
in peripheral frequency selectivity, we measured auditory filter shapes in the same subjects, using
the notched-noise method, also as a function of level. We then used the derived filter shapes to
predict performance in the F0DL task in the same subjects. Model predictions provided a good
description of the data, provided certain assumptions were made about the nature of the F0
detection processes. We have recently collected similar data from hearing-impaired listeners
who have broader auditory filters. The results are in good agreement with the prediction is that
broader auditory filters will lead to a lowering in the harmonic number at which F0DL performance
begins to deteriorate for a given bandpass region.
B. Reintroducing low-frequency fine structure in simulations of cochlear-implant
processing
We have recently shown that cochlear-implant processing results in greatly impaired pitch
processing, including the inability to use pitch differences in perceptually segregating competing
sources. The question was whether reintroducing some low-frequency fine-structure information
might enable subjects to make use of F0 differences to help with segregation. This question is
not only of theoretical interest, but has practical implications: many recent cochlear implantees
have some residual (usually low-frequency) hearing in the non-operated ear. Also, there has
been some interest in short-insertion cochlear implants, where residual hearing in the apical part
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Chapter 38. Auditory Perception and Cognition
of the implanted cochlea can be preserved. Results from our study suggest that even a small
amount of residual hearing (> 300 Hz) can improve performance, both for sentence recognition
and for concurrent-vowel identification. This provides encouragement for strategies that involve
combining a cochlear implant with a hearing aid, in order to improve speech reception in noisy
backgrounds.
C. Detection and discrimination of harmonic tone complexes in the presence of other
competing tone complexes
Decades of research have gone into understanding how the pitch of a single complex tone is
processed by the auditory system. In contrast, studies of pitch perception involving more than
one complex tone are very rare. This is an important omission, in that it is relatively rare that
sounds we encounter in our everyday environment are presented in total isolation. This study
marks a first step in systematically studying the conditions in which the pitch of one complex is
perceived in the presence of another. One important observation is that many models of pitch
perception rely on spectrally resolved harmonics. While such harmonics may be resolved when
presented in isolation, considerably fewer harmonics will be resolved when more than one
complex tone is presented at a time. Our experiments involve three stages: first, the F0DLs for a
complex in isolation is measured; second, the detection threshold of one complex in the presence
of another is measured; third the signal-to-interferer threshold is measured for achieving F0
discrimination at level 2 or 4 times higher than that found for a complex in quiet. By using equalamplitude harmonic complexes in random and sine phase within a fixed spectral bandwidth, we
can carefully control for the peripheral resolvability of individual components. Our results provide
strong tests for models of pitch, in that spectrally-based models would predict a breakdown in
performance once no resolved harmonics are present, whereas temporal models are generally
less reliant on spectral resolvability.
D. Functional anatomy of pitch perception and auditory stream segregation
Recent work has shown areas of anterior lateral Heschl’s gyrus are sensitive to stimulus
regularity, in that more periodic sounds elicit greater activity, as measured using techniques such
as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI).
Similar changes can also be observed in the brainstem. The question we posed, in collaboration
with Dr. Jennifer Melcher of Mass. Eye and Ear Infirmary (MEEI), was whether this increase in
activity reflected increased physical stimulus regularity or whether it more closely followed
changes in perceived pitch salience. We addressed this question by measuring the blood
oxygenation level difference (BOLD) responses to harmonic tone complexes that contained either
resolved or unresolved harmonics. The reasoning was that all the stimulus were equally regular
in their temporal structure, but that the unresolved harmonic complexes had a much weaker pitch
salience. Other conditions controlled for the effect of spectral region and F0, independent of
resolvability. The fMRI results showed a marked reduction in activation in antero-lateral Heschl’s
gyrus for the condition containing only unresolved harmonics. However, a similar reduction was
not observed in the brainstem. This suggests that the auditory cortical activity reflects pitch
salience rather than stimulus regularity per se, and further suggests a hierarchy of processing,
whereby the brainstem responses may reflect more the physical stimulus attributes rather than
the percept.
Publications
Journal Articles, Published
Oxenham, A. J., Bernstein, J. G. W., and Penagos, H. (2004). “Correct tonotopic representation is
necessary for complex pitch perception,” Proc. Natl. Acad. Sci. USA 101, 1421-1425.
Penagos, H., Melcher, J. R., and Oxenham, A. J. (2004). “A neural representation of pitch
salience in non-primary human auditory cortex revealed with fMRI,” J. Neurosci. 24, 6810-6815.
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Micheyl, C., and Oxenham, A. J. (2004). “Sequential F0 comparisons between resolved and
unresolved harmonics: No evidence for translation noise between two pitch mechanisms,” J.
Acoust. Soc. Am. 116, 3038-3050.
Oxenham, A. J., and Dau, T. (2004). “Masker phase effects in normal-hearing and hearingimpaired listeners: Evidence for peripheral compression at low signal frequencies,” J. Acoust.
Soc. Am. 116, 2248-2257.
Journal Articles, Accepted for Publication
Oxenham, A. J., and Ewert, S. (2005). “Estimates of auditory filter phase response at and below
characteristic frequency,” Journal of the Acoustical Society of America (forthcoming).
Rosengard, P. S., Oxenham, A. J., and Braida, L. D. (2005). “Comparing different estimates of
cochlear compression in listeners with normal and impaired hearing,” Journal of the Acoustical
Society of America (forthcoming).
Bernstein, J. G., and Oxenham, A. J. (2005). “An autocorrelation model with place dependence to
account for the effect of harmonic number on fundamental frequency discrimination,” Journal of
the Acoustical Society of America (forthcoming).
Gutschalk, A., Micheyl, C. Melcher, J. R., Rupp, A., Scherg, M., and Oxenham, A. J. (2005).
“Neuromagnetic correlates of streaming in human auditory cortex,” Journal of Neuroscience
(forthcoming).
Micheyl, C., and Oxenham, A. J. (2005). “Comparing F0 discrimination in sequential and
simultaneous conditions,” Journal of the Acoustical Society of America (forthcoming).
Qin, M. K., and Oxenham, A. J. (2005). “Effects of envelope-vocoder processing on F0
discrimination and concurrent-vowel identification” Ear and Hearing (forthcoming).
Journal Articles, Submitted for Publication
Oxenham, A. J., and Simonson, A. M. (2005). “Level dependence of auditory filters in
nonsimultaneous masking as a function of frequency,” Journal of the Acoustical Society of
America (in revision).
Qin, M. K., and Oxenham, A. J. (2005). “Effects of introducing unprocessed low-frequency
information on the reception of envelope-vocoder processed speech,” Journal of the Acoustical
Society of America (in revision).
Bernstein, J. G., and Oxenham, A. J. (2005). “The relationship between harmonic resolvability
and pitch discrimination: Effects of stimulus level,” Journal of the Acoustical Society of America
(in revision).
Chapters in Books
Oxenham, A. J., Bernstein, J. G., and Micheyl, C. (2004). “Pitch perception of complex tones
within and across ears and frequency regions,” in Auditory Signal Processing: Physiology,
Psychoacoustics, and Models, Eds. D. Pressnitzer, A. de Cheveigné, S. McAdams, and L. Collet
(Springer, New York).
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Chapter 38. Auditory Perception and Cognition
Dau, T., Ewert, S., and Oxenham, A. J. (2004). “Effects of concurrent and sequential streaming in
comodulation masking release,” in Auditory Signal Processing: Physiology, Psychoacoustics, and
Models, Eds. D. Pressnitzer, A. de Cheveingné, S. McAdams, and L. Collet (Springer, New York).
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